1904cc Engine Build

[I Ride Dirt]

So I have a 1965 baja that I have been dd for a while, and the engine is tired. I have an AH case that's been that's been sitting around and is tapped out for full flow, and cut for 90.5's. My plan is to build a 1904cc with a bit of mild performance and decent gas mileage. I have been doing some research and have found CB's "Gas Saver" motor, and I have decided to use that as kind of a base for my build. I was planning on throwing a w110 in but some people have said the idle quality isn't too great with the Weber ICT's. Has anyone ever used the "Gas Saver" motor? What are their thoughts on it? What are some of your similar builds/opinions? Here is my build so far:

1904cc
74mm 4140 CW Crank
Gas Saver Special Grind Cam from Eagle
Ultralight 28mm matching lifters
Stock heads
Aluminum Pushrods
Stock 1.1:1 rockers
90.5 P&C
Dual 34 ICT Baby Webers
Lightened Flywheel
26mm Oil Pump from CB
Elevation is 4800 ft

Not trying for performance, but would like to roast some occasional Hondas..
What do ya'll think?

Here's a link to CB's Gas Saver motor: http://www.cbperformance.com/product-p/1179.htm

[oldspeedsi]

Honestly that should be a pretty good combo. You could always add ratio rockers if the top end is not enough.

[66brm]

40idf carbs.....
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Aust. RHD 66 Type 1
Aust. RHD 57 Type 1 Oval

[modok]

Looks good for a baha with big tires!

some form of bigger carbs and a engle 100 or web 218/119 cam you would have noticeably more power, but should you?? maybe, maybe not. On the trails I'd rather have it your way; tractor!!

The gas saver I think is same as the cheater but on wider lobe separation. For larger CC.....I think it is better to keep the LC at 107, so, I'd recommend the "normal" cheater instead.

[FreeBug]

I think CB's "gas saver" combo is a 1955, with the 76 mm crank. Any reason you're using 74 and not 76? I assume they have a pretty good combo already sorted out.

I've used that cam, and I liked it, but I think you will find it easier to set up with dual 40 IDFs, as suggested above.

[I Ride Dirt]

[marlin1893]

Just built a 1904 and still trying to figure out the single 44IDF not sure about drilling so it will idle without having the throttle blades slightly open. Have a 110 cam and she will only idle with the idle screw in at least 1.5 turns and that opens the throttle blades slightly. Be careful if you go with a 76mm crank as I had to shim my cylinders .0100 to get deck height and that extra 2 mm will need more. As it is I'm at 8.6 to1 so if you are building a lower comp engine you will need more shim height. I'm no expert at all so check with the guys that really know. I thought you needed "B" pistons when you go above 74-76 mm stroke like when you go with an 82mm you can't use the "A" pistons??

[I Ride Dirt]

[ALB]

If you use 5.325" rods with a 74mm crankshaft and A pistons you'll find it finishes up just a hair (maybe 2 hairs?) wider than stock instead of almost 1/4" if you used stock length (5.4") rods. With a 76mm crank the engine would normally be a little over 1/4" (7mm) wider with stock rods and A pistons; using the shorter rods subtracts .075" (almost 2mm) from each side. You could use short rods (again, with A pistons) on a 78mm crank as well, for a great baja bug engine. Be sure to mock up the engine first and do any piston skirt clearancing (they will hit the crank) before having them balanced.

As usual, just my 2 1/2 cents (I'm Canadian, eh). Al
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On a lifelong mission to prove (much to my wife's dismay) that Immaturity is Forever!!

[I Ride Dirt]

[modok]

Good question.
I "think" the idea with the "gas saver" on 112 LC, is you have a bit less overlap and a few degrees later intake close point, which, as a general rule.....less overlap well reduce reversion at part throttle (good for MPG), and the later IC point might allow a few tenths higher CR(good for MPG).

HOWEVER, the timing is so short anyway, I don't actually know if the general rules really should apply.

Another general rule is: the more CC you put under a given head, the more overlap it NEEDS (and the more it will tolerate)

Also, the compression ratio will just have to be under 8-1 either way, because they are just really short cams.

IMO, if it was only 1500-1800cc, and single carb the gas saver would definitely save gas, BUT, with duals on short manifolds and larger CC, I don't think it's called for, so I'd use the cheater.

If you got the 40x35.5 valve heads like in the CB kit, THEN you'd want the gas saver.
What will really happen...I don't know, does anyone? Pat Downs might.

[modok]

dang you made me think hard
But anyway, yeah I think I got it.
Why CB used the 112 LC and you probably should not; It' the big valve heads.

[I Ride Dirt]

[marlin1893]

This is the first I have heard of needing to clearance the piston skirts on a 74mm crank? I used a set of new Germany rods and a clearanced block plus shimmed my cyl .060 plus .040 copper head gaskets to get aprox 8.5 CR. Comp test came in aprox 144-152 psi. Can't get a good idle with no holes drilled in throttle plates I'm using the center mount 44 IDF kit from Webers Direct. I was advised to drill air to 2.00 and mains to 1.60 my idle are still @ .55 and am using F7 tubes that came with it. It will idle at 400-500 but as soon as I try to idle up the throttle plates start to open and it runs rough. Lots of guys here say NOT to drill 1.50-2.00 holes so I am trying to tune without that first. Anyone know from experience how to do this ???

[modok]

I have run 90.5 mahle A pistons with a 78 stroke crank, they did not hit, but it is true some combinations of parts will.

[babyblue69]

How did the engine come out? I am looking at building the same motor for my Ghia for commuting on flat land here in central California.

[I Ride Sand]

we ended up waiting and still have not built it. the crank needs to be ground .001" on the center main. we decided to throw together a 1641 out of used parts while we wait and have just not had time to get to it. check back in spring!

hey modok, think i can get away throwing that crank on centers and polishing it down with a strip of emery cloth? or should it be done with a real crank polisher? .001" is all that is stopping us from building this thing right now (plus som indecisiveness on upgrading the heads)

[modok]

Possibly. I think it could be done certainly with a lathe, abrasive paper, and may want a backer of form, like a springy slim jim or packing strap that is the right width, this is to avoid taper and/or taking out more by the oil holes, which can be a problem since these cranks have big oil holes and often troughs. My crank guy would shave it for 50$, and I'd polish it for half that, but polishing doesn't have a lot of control over shape....if you know what I mean.

[ALB]

[I Ride Sand]